Interface Definition:

An interface is a device or a system that allows two or more unrelated entities to communicate with each other. The remote control is an interface between you and television, the English language is an interface between two individuals, and military etiquette is an interface between persons of different ranks, according to this definition.

An interface (as defined in the glossary) is a type in the Java programming language, just like a class. Interfaces define methods in the same way that classes do. An interface, unlike a class, never implements methods; instead, the methods described by the interface are implemented by the classes that implement it. A single class can implement many interfaces.

The bicycle class and hierarchy define what a bicycle can and cannot do in terms of “bicycleness.” Bicycles, on the other hand, engage with the world differently. An inventory program, for example, may keep track of a bicycle in a store. An inventory program is unconcerned with the type of objects it handles as long as each one provides particular data, such as a price and a tracking number.

Rather than imposing class links on totally unrelated goods, the inventory program establishes a communication protocol. This protocol is implemented as a set of method definitions within an interface. Methods to set and get the retail price, assign a tracking number, and so on would be defined but not implemented in the inventory interface.

The bicycle class must accept this protocol by implementing the interface to participate in the inventory program. When a class implements an interface, it promises to implement all of the interface’s methods. The bicycle class would then include implementations for methods such as setting and getting the retail price, assigning a tracking number, and so on.

You utilize an interface to design a behavior protocol that any class in the hierarchy can implement. The following applications benefit from interfaces:

Without arbitrarily creating a class relationship, capturing commonalities between unconnected classes.

Defining methods that one or more classes should implement:

• The programming interface of an object is shown without revealing its class.
• Numerous inheritance is a feature of various object-oriented languages that allows a class to have multiple superclasses.